The invention relates to a position sensor for forming, using optical means, an electric signal which is dependent on the position of an end of a pointing member which bears on the position sensor.
2. Description of the Prior Art
A position sensor of this kind is known from a publication by S. Tamura et al in Applied Optics, Vol. 19, No. 11, June 1, 1980. The described sensor is formed by a rectangular flat plate which is surrounded by oppositely situated rows of light-emitting and detecting diodes. An end of a pointing member, for example, a stylus positioned on the flat plate "interrupts" the light which is emitted by the rows of diodes in a given sequence and which is detected more or less by the oppositely situated diodes. Each photodiode should be connected to a so-called coherent detection circuit; consequently, a sizable position sensor offering a suitable resolution is an expensive device. Furthermore, the resolution and the absolute size of the position sensor are restricted by the low directional sensitivity of the photodiodes and also by the minimum signal-to-noise ratio required.